The present invention relates to an apparatus for position information, comprising a satellite assisted position measuring device with a power drawing measurement mode, in which it provides the present position of the apparatus at an output, and a power saving idle mode, a mobile radio network assisted communication device connected to said output for the purpose of sending the position via a cellular mobile radio network, where the communication device provides the local reception field strength and the local cell identifier of the mobile radio network at an interface.
The invention also relates to a method for position information using such position measuring and communication devices.
Combined satellite navigation and mobile radios are used for tracking freight or in fleet management, for example. A large problem in this context is the high power consumption of the known apparatuses, because particularly in the case of mobile freight, such as containers, refrigerated containers, etc., an onboard power supply is not always available.
Alternative supplies using solar cells and storage batteries have therefore already been proposed. Particularly in the logistics sector, however, there are often long stationary times in the dark, for example in a warehouse, on an unlit siding, etc., which would require extremely large storage batteries.
EP 1 132 713 discloses a position information apparatus of the type cited in the introduction in which the satellite assisted position measuring device is a GPS receiver which can be put into a power saving idle mode (“standby”). EP 1 132 713 proposes putting the GPS receiver into the measurement mode only when, by way of example, a key on the communication device (a mobile telephone) is pressed, a particular number is dialed, a call is received on the mobile telephone, the mobile telephone is outside of its reception range or a timer expires. The first variants require the user to actively take action in order to initiate the position finding, while the variant with the timer results in a periodic power consumption in the GPS receiver.
The aim of the invention is to develop an apparatus and a method for position information further such that they have a particularly low average power requirement under practical conditions of use. In a first aspect of the invention, this aim is achieved with an apparatus of the aforementioned type which is distinguished by a control device which is connected to the output of the position measuring device and to the interface of the communication device and which, in the event of a change in the reception field strength which exceeds a threshold value or in the event of a change in the cell identifier, switches the position measuring device to the measurement mode and, if the position remains the same over a prescribed period, switches the position measuring device to the idle mode.